Air springs are modeled in ADAMS/Chassis with 3-D Splines. In an air spring spline, X is spring deflection (X=0 represents the trim position), Y is spring force, and Z is trim load. The 3-D Spline represents the entire operating range of the air spring.
To model an airspring with ADAMS/Chassis, you must specify a 3-D Spline, the trim load of the air spring, and the upper and lower attachment points of the air spring.
The format of the 3D spline is very important, see the following document for an example of taking test data and creating the spline.
To add air springs to your model, you must select an Air spring property file for your spring property file, and add hardpoints 'airspring_seat_upper' and 'airspring_seat_lower' to your subsystem file.
Air Spring property files are stored in the springs.tbl subdirectory of a vehicle database.
The Air spring property file contains the 3-D spline information and the trim length of the airspring.
The subsystem file contains the Trim Load, or activates the Auto Trim Load option. With the Trim Load option, a single trim load is used throughout the simulation. With the Auto Trim Load option, the trim load is continuously calculated by ADAMS/Solver.
Trim Load - Load in spring
when the suspension is at trim height.
Trim Length - Distance between the upper and lower spring seats when
the suspension is at trim height
|
Note: The air spring spline must be constructed in a certain way, the Z values (trim loads) must match the Y values corresponding to X = 0. See numbers in bold. |
Attachment options for air springs are the same as coil springs, based on suspension type.
SPLINE/300 ,X= -1.0000e+02,-9.5000e+01,-9.0000e+01,-8.5000e+01,-8.0000e+01 , -7.5000e+01,-7.0000e+01,-6.5000e+01,-6.0000e+01,-5.5000e+01 , -5.0000e+01,-4.5000e+01,-4.0000e+01,-3.5000e+01,-3.0000e+01 , -2.5000e+01,-2.0000e+01,-1.5000e+01,-1.0000e+01,-5.0000e+00 , 0.0000e+00, 5.0000e+00, 1.0000e+01, 1.5000e+01, 2.0000e+01 , 2.5000e+01, 3.0000e+01, 3.5000e+01, 4.0000e+01, 4.5000e+01 , 5.0000e+01, 5.5000e+01, 6.0000e+01, 6.5000e+01, 7.0000e+01 , 7.5000e+01, 8.0000e+01, 8.5000e+01, 9.0000e+01, 9.5000e+01 , 1.0000e+02 ,Y= 4959 , 2.6640e+03, 2.7800e+03, 2.8830e+03, 2.9770e+03, 3.0650e+03 , 3.1500e+03, 3.2350e+03, 3.3220e+03, 3.4110e+03, 3.5060e+03 , 3.6050e+03, 3.7110e+03, 3.8240e+03, 3.9430e+03, 4.0690e+03 , 4.2010e+03, 4.3410e+03, 4.4860e+03, 4.6380e+03, 4.7950e+03 , 4.9590e+03, 5.1270e+03, 5.3010e+03, 5.4810e+03, 5.6670e+03 , 5.8590e+03, 6.0590e+03, 6.2670e+03, 6.4850e+03, 6.7150e+03 , 6.9590e+03, 7.2200e+03, 7.5000e+03, 7.8040e+03, 8.1350e+03 , 8.5000e+03, 8.9020e+03, 9.3480e+03, 9.8440e+03, 1.0399e+04 , 1.1021e+04 ,Y= 6524 , 3.6130e+03, 3.7630e+03, 3.8950e+03, 4.0160e+03, 4.1290e+03 , 4.2390e+03, 4.3470e+03, 4.4570e+03, 4.5710e+03, 4.6910e+03 , 4.8160e+03, 4.9500e+03, 5.0920e+03, 5.2420e+03, 5.4000e+03 , 5.5680e+03, 5.7430e+03, 5.9270e+03, 6.1190e+03, 6.3180e+03 , 6.5240e+03, 6.7370e+03, 6.9580e+03, 7.1850e+03, 7.4210e+03 , 7.6640e+03, 7.9170e+03, 8.1790e+03, 8.4550e+03, 8.7440e+03 , 9.0500e+03, 9.3760e+03, 9.7260e+03, 1.0104e+04, 1.0515e+04 , 1.0965e+04, 1.1460e+04, 1.2007e+04, 1.2615e+04, 1.3292e+04 , 1.4048e+04 ,Y= 8081 , 4.5550e+03, 4.7410e+03, 4.9070e+03, 5.0570e+03, 5.1970e+03 , 5.3310e+03, 5.4640e+03, 5.5980e+03, 5.7360e+03, 5.8800e+03 , 6.0310e+03, 6.1920e+03, 6.3620e+03, 6.5420e+03, 6.7330e+03 , 6.9340e+03, 7.1440e+03, 7.3650e+03, 7.5940e+03, 7.8330e+03 , 8.0810e+03, 8.3360e+03, 8.6010e+03, 8.8740e+03, 9.1560e+03 , 9.4470e+03, 9.7500e+03, 1.0064e+04, 1.0393e+04, 1.0739e+04 , 1.1105e+04, 1.1494e+04, 1.1911e+04, 1.2361e+04, 1.2851e+04 , 1.3386e+04, 1.3974e+04, 1.4625e+04, 1.5347e+04, 1.6152e+04 , 1.7050e+04
Adding a Second Set
To use a second set of air springs in the model, edit your subsystem data file and add a second SpringPair .xml block. You also must add 'airspring_seat_upper2' and 'airspring_seat_lower2' hardpoint pairs.